Brockton Fire Chief Richard C. Francis said a preliminary investigation indicates the fire started when a lawn mower malfunctioned igniting gasoline also stored in shed, the Enterprise reported. The flames climbed the metal structure, known as the postal center annex building, and caught inside, he said.

The call came in at 7:53 a.m. and firefighters from Brockton and West Bridgewater responded to the postal center at 220 Liberty St. near the town line.

There were no injuries, and Chief Frances said he has not heard any reports of mail being damaged.

Maintenance workers were unable to control the blaze when it erupted, and instead sounded the alarm. Employees were evacuated from the building. A fire official said one of the exits near the shed where the fire began is usually used as an emergency exit, but a maintenance worker stayed by the door directing workers to use another exit.

At 9:30 a.m. close the 30 firefighters were still on the scene pulling the metal paneling from the side of the approximately 60 by 100 feet annex building to make sure there was no lingering burn in the siding.

"It's very labor intensive getting the panels off the side," Chief Francis said, because they overlap and are screwed into each other.

Firefighters were tearing apart the charred siding using power saws and axes. Providence-based Firefighter Canteen had a vehicle on scene to help keep them hydrated while doing the difficult work.

Postal employees were still on scene milling about on the far side of the building from where the fire started. A Postal Service official declined to comment on the incident.